Foodborne infections of enteric origin constitute a significant segment of diseases that affect humans. Despite many control strategies adopted, foodborne infections invite public health concerns worldwide. Among the foodborne outbreaks in the United States, non-typhoidal salmonellosis ranks very high among its competitors. Some of the major serotypes of Salmonella that cause non-typhoidal foodborne infections include Salmonella enterica serovar Enteritidis, Salmonella enterica serovar Typhimurium, and Salmonella enterica serovar Heidelberg. Poultry and poultry products are significant contributors of foodborne salmonellosis in humans. Salmonella colonizes the cecum of poultry and results in fecal excretion of the pathogen to the environment. Also, the pathogen can invade internal organs such as liver and spleen, and could be deposited in eggs during its formative stage. Among the Salmonella serotypes, Salmonella enterica serovar Heidelberg has emerged to cause multiple foodborne outbreaks associated with poultry products, recently. The pathogen has acquired resistance to commonly used antibiotics such as gentamicin, streptomycin, tetracycline, and ampicillin. Antimicrobial interventional strategies targeting the control of Salmonella enterica serovar Heidelberg is an emergent need. Given the situation that the bacteria are multidrug resistant (MDR), and that the Food and Drug Administration (FDA) has issued restrictions on the use of medically important antibiotics in animal agriculture, alternative strategies that can control the pathogen are required. Probiotics could be an alternative to antibiotics, as they can competitively exclude pathogens from attaching to intestinal epithelium thereby maintaining normal gut microbiota. Among the many probiotics, host-derived Lactobacillus could play a major role as they have an intrinsic affinity towards the host epithelium. In this thesis project, we investigated the potential of turkey gut-derived Lactobacillus ingluviei and Lactobacillus salivarius as an alternative strategy to control MDR Salmonella enterica serovar Heidelberg in turkey poults. We designed two objectives: 1. to determine the effect of supplementation of turkey gut-derived Lactobacillus salivarius and Lactobacillus ingluviei in combination against MDR Salmonella enterica serovar Heidelberg colonization in turkey poults, and 2. to determine the probiotic qualities of turkey gut-derived Lactobacillus salivarius and Lactobacillus ingluviei isolates in vitro. At first, we determined the efficacy of Lactobacillus of turkey-gut origin (Lactobacillus salivarius and Lactobacillus ingluviei) against MDR Salmonella enterica serovar Heidelberg colonization in commercial straight-run Hybrid Converter turkey poults. Three independent experiments were conducted. The treatment groups were negative control (-S. enterica serovar Heidelberg, -Lactobacillus), S. enterica serovar Heidelberg control (+S. enterica serovar Heidelberg, -Lactobacillus), and a treatment group (+S. enterica serovar Heidelberg, +Lactobacillus), with at least nine birds in each treatment group per experiment. Lactobacillus (8 log10 CFU/gallon of water) was supplemented through drinking water continuously for 14 days. Poults were challenged with the 2011 turkey outbreak strain of Salmonella enterica serovar Heidelberg (5.0 log10 CFU/ml) on day 7, and Salmonella enterica serovar Heidelberg counts were determined on days 2 and 7 post-inoculation. Results indicated that the treatments significantly reduced MDR Salmonella enterica serovar Heidelberg in the cecum, liver, and spleen of turkey poults compared to the Salmonella enterica serovar Heidelberg control in two of the three experiments conducted (P<0.05). In the follow-up study, we determined the qualities of Lactobacillus ingluviei and Lactobacillus salivarius to be considered as potential probiotics, in vitro. Although turkey gut-derived, any potential probiotic strain will face a series of physiological challenges until efficient colonization in the cecum, once administered orally. These obstacles include the low acid environment in the gizzard, and the detergent action of bile and bile salts, before its colonization in the lower part of the intestine. Once these obstacles are traversed, the probiotic strain should have the ability to colonize strongly to the intestinal epithelium for performing colonization resistance against invading pathogens. In this process, potential probiotic strains will induce strong antimicrobial property. Our studies indicated that both Lactobacillus exerted significant resistance to low pH and bile salts (P<0.05). Our cell culture studies indicated that the tested Lactobacillus isolates had high adhesion to model avian intestinal epithelial cells, validating the in vivo studies. Moreover, the cell-free extracts of Lactobacillus salivarius and Lactobacillus ingluviei showed high antimicrobial activity separately against three major serotypes of Salmonella, namely, Salmonella enterica serovar Enteritidis, Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Heidelberg (P<0.05). We also tested the antibiotic susceptibility of the Lactobacillus isolates. Lactobacillus salivarius and Lactobacillus ingluviei were sensitive to a variety of commonly used antibiotics for human therapy. The overall results indicated that turkey gut-derived Lactobacillus (Lactobacillus salivarius and Lactobacillus ingluviei) could be an effective strategy to reduce MDR Salmonella enterica Heidelberg colonization in turkeys, potentially improving the microbiological safety of turkey products.
University of Minnesota M.S. thesis. May 2017. Major: Animal Sciences. Advisor: Anup Kollanoor Johny. 1 computer file (PDF); xiv, 93 pages.
Vazhakkattu Thomas, Jijo.
Determining the Probiotic Potential of Turkey Gut-Derived Lactobacillus against Multidrug-Resistant Salmonella enterica serovar Heidelberg in Turkey Poults.
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